The present invention relates to a magnetic core and an induction device having the magnetic core.
Induction devices such as reactors or transformers, which are configured by winding a coil around a magnetic core, are conventional. Some of such induction devices have a magnetic core employing a ferrite core and a dust core in combination. See, for example, Japanese Laid-Open Patent Publication No. 2007-95914.
A core described in the aforementioned document includes an E-shaped core having three magnetic legs and a flat plate-like I-shaped core having a pair of cutout portions. Two of the magnetic legs arranged at opposite ends of the E-shaped core are joined to the cutout portions of the I-shaped core. This configuration facilitates positioning the E-shaped core with respect to the I-shaped core when the E-shaped core is attached to the I-shaped core.
In the above-described core, if the I-shaped core is formed using a ferrite core and the E-shaped core, around which a coil is wound, is formed by a dust core, the cross-sectional area of a portion where the coil is wound and the winding length of the coil are expected to be reduced. However, if each of the magnetic legs of the dust core contacts the ferrite core by a small contact area, magnetic flux saturation may occur in a portion of the ferrite core that contacts the dust core. This may make it impossible to obtain desirable direct current superimposing characteristics.
To solve this problem, in the core described in the aforementioned document, the distal surface and the corresponding side surface of each of the magnetic legs of the dust core may be held in contact with the corresponding one of the cutout portions to increase the contact area between the magnetic leg and the cutout portion. However, when the two magnetic legs are joined to the cutout portions as in the case of the aforementioned document, the interval between the magnetic legs must be greater than the interval between the cutout portions to facilitate mounting the dust core. This makes it difficult to hold the distal surfaces and the side surfaces of all the magnetic legs in contact with the ferrite core in the above-described document. As a result, it is impossible to ensure a sufficiently large contact area between the cores.